igneous

Granite

Granite (Felsic Intrusive Igneous Rock)

Hardness: 6-7 on Mohs scale; Color: typically mottled grey, white, pink, and black; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained) crystalline; Cleavage: none (though component minerals have their own); Specific Gravity: 2.63 to 2.75.

Hardness: 6-7 on Mohs scale
Color: typically mottled grey, white, pink, and black
Luster: Dull to vitreous

Identified March 23, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground (plutonic). Found in continental crust; ages can range from billions of years (Precambrian) to relatively recent mountain-building events.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and memorial monuments. Also used as crushed stone for road base and railroad ballast.

Geological facts

Granite makes up the majority of the Earth's continental crust. It is the primary rock found in iconic locations like Yosemite National Park's Half Dome and Mount Rushmore.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and large, interlocking mineral crystals (visible quartz, feldspar, and mica). Found globally in mountainous regions or where ancient shield rocks are exposed. Collectors look for unique color variations or large crystal inclusions.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous